This project will investigate the clinical application of a low-energy brief-stimulus (LEBS) for use in unilateral electroconvulsive therapy (ECT). The initial phase will establish the clinical efficacy of the LEBS as compared to a standard ECT stimulus. The anti-depressant effect will be measured by the Wakefield Self-assessment scale, a Standardized Interview, a Behavioral Measurement technique and a team concensus rating of progress. The Halstead- Reitan neuropsychological battery will be used to evaluate organic side effects. The second phase will investigate the combinations of stimulus parameters (pulse width, pulse energy, number of pulses, and interpluse interval) which will produce clinically effective results at the minimal energy per treatment. The objective is to specify the stimulus as accurately as possible. The third phase will investigate the relative effectiveness of unilateral vs bilateral electrode placement for the LEBS stimulus in an attempt to combine the greater effectiveness of bilateral ECT with the reduced side effects of unilateral ECT.